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Add boundary and overflow checks to the formulas used in the TCP CUBIC

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congestion control module.

Submitted by:		Richard Scheffenegger
Reviewed by:		rgrimes@
Differential Revision:	https://reviews.freebsd.org/D19118
This commit is contained in:
Michael Tuexen 2019-11-16 12:00:22 +00:00
parent b0c1a13e4e
commit c968c769af
2 changed files with 42 additions and 11 deletions
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24
sys/netinet/cc/cc_cubic.c
View File

@ -52,6 +52,7 @@ __FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/limits.h>
#include <sys/malloc.h>
#include <sys/module.h>
#include <sys/socket.h>
@ -140,7 +141,14 @@ cubic_ack_received(struct cc_var *ccv, uint16_t type)
cubic_data->min_rtt_ticks == TCPTV_SRTTBASE)
newreno_cc_algo.ack_received(ccv, type);
else {
ticks_since_cong = ticks - cubic_data->t_last_cong;
if ((ticks_since_cong =
ticks - cubic_data->t_last_cong) < 0) {
/*
* dragging t_last_cong along
*/
ticks_since_cong = INT_MAX;
cubic_data->t_last_cong = ticks - INT_MAX;
}
/*
* The mean RTT is used to best reflect the equations in
@ -159,12 +167,14 @@ cubic_ack_received(struct cc_var *ccv, uint16_t type)
ccv->flags &= ~CCF_ABC_SENTAWND;
if (w_cubic_next < w_tf)
if (w_cubic_next < w_tf) {
/*
* TCP-friendly region, follow tf
* cwnd growth.
*/
CCV(ccv, snd_cwnd) = w_tf;
if (CCV(ccv, snd_cwnd) < w_tf)
CCV(ccv, snd_cwnd) = ulmin(w_tf, INT_MAX);
}
else if (CCV(ccv, snd_cwnd) < w_cubic_next) {
/*
@ -172,12 +182,14 @@ cubic_ack_received(struct cc_var *ccv, uint16_t type)
* cwnd growth.
*/
if (V_tcp_do_rfc3465)
CCV(ccv, snd_cwnd) = w_cubic_next;
CCV(ccv, snd_cwnd) = ulmin(w_cubic_next,
INT_MAX);
else
CCV(ccv, snd_cwnd) += ((w_cubic_next -
CCV(ccv, snd_cwnd) += ulmax(1,
((ulmin(w_cubic_next, INT_MAX) -
CCV(ccv, snd_cwnd)) *
CCV(ccv, t_maxseg)) /
CCV(ccv, snd_cwnd);
CCV(ccv, snd_cwnd));
}
/*

29
sys/netinet/cc/cc_cubic.h
View File

@ -41,6 +41,8 @@
#ifndef _NETINET_CC_CUBIC_H_
#define _NETINET_CC_CUBIC_H_
#include <sys/limits.h>
/* Number of bits of precision for fixed point math calcs. */
#define CUBIC_SHIFT 8
@ -70,6 +72,12 @@
/* Don't trust s_rtt until this many rtt samples have been taken. */
#define CUBIC_MIN_RTT_SAMPLES 8
/*
* (2^21)^3 is long max. Dividing (2^63) by Cubic_C_factor
* and taking cube-root yields 448845 as the effective useful limit
*/
#define CUBED_ROOT_MAX_ULONG 448845
/* Userland only bits. */
#ifndef _KERNEL
@ -172,7 +180,12 @@ cubic_cwnd(int ticks_since_cong, unsigned long wmax, uint32_t smss, int64_t K)
/* K is in fixed point form with CUBIC_SHIFT worth of precision. */
/* t - K, with CUBIC_SHIFT worth of precision. */
cwnd = ((int64_t)(ticks_since_cong << CUBIC_SHIFT) - (K * hz)) / hz;
cwnd = (((int64_t)ticks_since_cong << CUBIC_SHIFT) - (K * hz)) / hz;
if (cwnd > CUBED_ROOT_MAX_ULONG)
return INT_MAX;
if (cwnd < -CUBED_ROOT_MAX_ULONG)
return 0;
/* (t - K)^3, with CUBIC_SHIFT^3 worth of precision. */
cwnd *= (cwnd * cwnd);
@ -183,9 +196,13 @@ cubic_cwnd(int ticks_since_cong, unsigned long wmax, uint32_t smss, int64_t K)
* CUBIC_SHIFT included in the value. 3 from the cubing of cwnd above,
* and an extra from multiplying through by CUBIC_C_FACTOR.
*/
cwnd = ((cwnd * CUBIC_C_FACTOR * smss) >> CUBIC_SHIFT_4) + wmax;
return ((unsigned long)cwnd);
cwnd = ((cwnd * CUBIC_C_FACTOR) >> CUBIC_SHIFT_4) * smss + wmax;
/*
* for negative cwnd, limiting to zero as lower bound
*/
return (lmax(0,cwnd));
}
/*
@ -223,8 +240,10 @@ tf_cwnd(int ticks_since_cong, int rtt_ticks, unsigned long wmax,
{
/* Equation 4 of I-D. */
return (((wmax * CUBIC_BETA) + (((THREE_X_PT3 * ticks_since_cong *
smss) << CUBIC_SHIFT) / TWO_SUB_PT3 / rtt_ticks)) >> CUBIC_SHIFT);
return (((wmax * CUBIC_BETA) +
(((THREE_X_PT3 * (unsigned long)ticks_since_cong *
(unsigned long)smss) << CUBIC_SHIFT) / (TWO_SUB_PT3 * rtt_ticks)))
>> CUBIC_SHIFT);
}
#endif /* _NETINET_CC_CUBIC_H_ */